Engine oil recirculation system for extended maintenance interval

ABSTRACT

An oil recirculation system includes an engine lubricated by a flow of oil through the engine, a supplemental oil tank arranged to contain a quantity of oil, an oil inlet conduit arranged to fluidly connect the supplemental oil tank and the engine, an oil outlet conduit arranged to fluidly connect the supplemental oil tank and the engine, a first pump operable to pump oil from the supplemental oil tank to the engine through the oil outlet conduit; and a second pump operable to pump oil from the engine to the supplemental oil tank through the oil inlet conduit. wherein the oil inlet conduit is coupled to the supplemental oil tank at a location above where the oil outlet conduit is coupled to the supplemental oil tank.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. application Ser. No. 14/453,048 filed Aug. 6, 2014, which claims priority to U.S. Provisional Application No. 61/894,156 filed Oct. 22, 2013, and U.S. Provisional Application No. 61/862,133 filed Aug. 5, 2013, all of which are incorporated herein by reference in their entireties.

BACKGROUND

Internal combustion engine oils, used as lubricants, lose their initial qualities after extended use and are thus no longer effective. Prolonged use causes the oil to degrade and lose its effectiveness due to an accumulation of combustion-generated solid debris and chemicals, accumulation of frictionally-generated metallic particles and a resulting drop in viscosity.

Due to this degradation over time, engine oils must be changed periodically. The frequency of these changes depends upon the usage patterns of the engine-driven equipment. For example, the oil in a homeowner's lawnmower engine may only need to be changed once per season. On the other hand, a commercial lawnmower engine may need to have its oil changed many times during a given season due to almost daily use of the equipment. These frequent oil changes lead to increased downtime of the equipment and increased costs to the users. The size of the sump in the engine may be increased to allow for a greater oil capacity (and hence greater oil life), but such an increase in size is not practical for many lawn and garden applications.

Accordingly, it would be advantageous to have an internal combustion engine with a supplemental oil reservoir capable of recirculating oil at given time intervals. This supplemental oil reservoir enables increased life of the oil in the system and therefore increased intervals between oil changes.

SUMMARY OF THE INVENTION

An embodiment relates to an oil recirculation system including an engine lubricated by a flow of oil through the engine, a supplemental oil tank arranged to contain a quantity of oil, an oil inlet conduit arranged to fluidly connect the supplemental oil tank and the engine, an oil outlet conduit arranged to fluidly connect the supplemental oil tank and the engine, a first pump operable to pump oil from the supplemental oil tank to the engine through the oil outlet conduit; and a second pump operable to pump oil from the engine to the supplemental oil tank through the oil inlet conduit. wherein the oil inlet conduit is coupled to the supplemental oil tank at a location above where the oil outlet conduit is coupled to the supplemental oil tank.

Another embodiment relates to a ride-on mower including an engine lubricated by a flow of oil through the engine, a supplemental oil tank arranged to contain a quantity of oil, a seat arranged to define a forward and a rearward direction of the ride-on mower, wherein the engine and the supplemental oil tank are located rearward of the seat, an oil inlet conduit arranged to fluidly connect the supplemental oil tank and the engine, an oil outlet conduit arranged to fluidly connect the supplemental oil tank and the engine, a first pump operable to pump oil from the supplemental oil tank to the engine through the oil outlet conduit, and a second pump operable to pump oil from the engine to the supplemental oil tank through the oil inlet conduit, wherein the oil inlet conduit is coupled to the supplemental oil tank at a location above where the oil outlet conduit is coupled to the supplemental oil tank.

Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an engine oil recirculation system in accordance with an exemplary embodiment;

FIG. 2 is a flowchart illustrating an engine oil recirculation method in accordance with an exemplary embodiment;

FIG. 3 is a perspective view of a mower with an engine oil exchange system in accordance with an exemplary embodiment;

FIG. 4a is a portion of a supplemental oil exchange system in accordance with an exemplary embodiment;

FIG. 4b is another view of the portion of a supplemental oil exchange system of FIG. 4 a;

FIG. 4c is another view of the portion of a supplemental oil exchange system of FIG. 4 a;

FIG. 4d is another view of the portion of a supplemental oil exchange system of FIG. 4 a;

FIG. 5 is a cross-sectional view of an engine having a supplemental oil exchange system in accordance with an exemplary embodiment;

FIG. 6 is another cross-sectional view of an engine having a supplemental oil exchange system in accordance with an exemplary embodiment;

FIG. 7 is a supplemental oil exchange system in accordance with another exemplary embodiment; and

FIG. 8 is another view of supplemental oil exchange system in accordance with an exemplary embodiment shown in FIG. 7.

Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

DETAILED DESCRIPTION

Referring to FIG. 1, an engine oil recirculation system 100 in accordance with an exemplary embodiment is shown. System 100 includes an internal combustion engine 102 having a driven shaft 103. Internal combustion engine 102 is preferably an air cooled general purpose engine, but may be any suitable oil-lubricated engine. Engine 102 includes a sump or reservoir 105 containing a sufficient amount of oil for lubrication of various components of the engine 102. As engine 102 is in operation, the oil in sump 105 is splashed, sprayed, or otherwise coated onto the components within engine 102 to lubricate and cool those components. Oil within sump 105 may be drained from engine 102 via a drain plug 107. In some embodiments, it is possible for engine 102 to have an oil fill opening (not shown) to enable the user to change or add oil to sump 105.

Fluidly coupled to engine 102 and sump 105 is a supplemental oil tank 104. Supplemental oil tank 104 is isolated from engine 102 and fluidly coupled to sump 105 via both an oil inlet conduit 110 and an oil outlet conduit 112. The locations of oil inlet conduit 110 and oil outlet conduit 112 are not limited to that which is shown in FIG. 1 and may be placed in any suitable location between supplemental oil tank 104 and sump 105. Supplemental oil tank 104 comprises a fill cap 117 that allows for refilling or replacement of oil in a reservoir 115 of supplemental oil tank 104. Supplemental oil tank 104 may also comprise a drain plug 116 for draining of oil from reservoir 115.

Oil inlet conduit 110 enables oil contained in reservoir 115 of supplemental oil tank 104 to be selectively and intermittently exchanged with the oil within sump 105 of engine 102. Prior to or concurrent with the exchange of oil from reservoir 115 to sump 105, some or all of the oil within sump 105 is pumped or otherwise drained from sump 105 via oil outlet conduit 112. For example, a pump 114 may be used to draw the oil out of sump 105 and into supplemental oil tank 104. This recently “used” oil from sump 105 is then mixed with a greater amount of supplemental oil within reservoir 115. A certain amount of supplemental oil from reservoir 115 is then added to sump 105 via oil inlet conduit 110. This supplemental oil may be added either via a gravity feed or via another pump 90 placed in-line with oil inlet conduit 110. A float system 118 may be configured to limit the amount of oil added to sump 105 by cutting off the flow of oil from reservoir 115 to sump 105 once the oil in sump 105 reaches a predetermined level. Additionally, while not shown, a vent line could be included between supplemental oil tank 104 and sump 105 such that the pressure levels within tank 104 and sump 105 are maintained substantially equal to one another.

FIG. 2 is a flowchart illustrating the process of oil recirculation in accordance with an exemplary embodiment. The process 200 begins with a determination if the engine 102 has been shut down at 202. If no, the process continues to determine if the engine 102 has been shut down. If yes, it is determined if a predetermined time period has elapsed at 204. If no, the process continues to determine if the predetermined time has elapsed. If yes, the oil recirculation functions described above with respect to FIG. 1 are initiated at 206. Then, at 208, it is determined whether either a predetermined amount of oil has been recirculated or a predetermined period of recirculation has passed. If no, the process continues to determine if one of these conditions exists. If yes, recirculation of oil is ended and the supplemental tank 104 and engine 102 are fluidly isolated at 210.

Using the above-described oil exchange system, the intervals between required oil changes for engine 102 can be substantially increased. Also, because the supplemental oil tank 104 and engine 102 are fluidly isolated from one another during operation of engine 102, there are no substantial alterations or limitations to engine 102. The system is not susceptible to tilting, etc., as may be the case if the system were to be fluidly coupled and in communication during certain points of engine operation.

Referring to FIG. 3, an engine oil recirculation system in accordance with another exemplary embodiment is disclosed. FIG. 3 shows a portion of a zero-turn radius lawnmower 300. One of ordinary skill in the art would recognize that elements of the lawnmower have been omitted for the sake of clarity. Lawnmower 300 comprises a frame 302 having a roll-over protection bar 304 mounted thereto. Roll-over protection systems (or ROPS) are commonly used on zero-turn and large riding mowers and tractors to protect the occupant in the event that the machine tips or rolls. In the exemplary embodiment, a supplemental oil tank 308 is coupled to or near roll-over protection bar 304 via a supplemental oil tank base 310 that is coupled to roll-over protection bar 304 or a nearby portion of frame 302. Supplemental oil tank 308 is mounted upon base 310 so as to be easily accessible by the operator or service mechanic. As will be further described herein below, oil from supplemental oil tank 308 is delivered to (and/or removed from) the oil sump of engine 306 via a conduit 312. Supplemental oil tank 308 may be a dedicated bottle specifically designed for the supplemental oil exchange system described. Alternatively, supplemental oil tank 308 may be a standard commercially-available bottle of oil, and base 310 may be configured so as to retain such a bottle. Regardless of the type of bottle used, the system enables the retrofitting of existing lawnmowers and engines with a supplemental oil exchange system that does not require costly engine block modifications or changes to the mower frame or other components.

FIGS. 4a-4d illustrate an engine oil recirculation system in accordance with another exemplary embodiment. System 400 comprises a bottle holder 402 that serves as the base for holding a commercially-available bottle 404 that contains oil. Oil bottle 404 is secured within bottle holder 402 via, for example, a platform 406 and a strap 408. However, other means of securing bottle 404 are also possible. Platform 406 may include at least one drain hole 428 which allows water, oil, or other fluids to be drained from the interior of bottle holder 402. Below oil bottle 404 but within the housing of bottle holder 402 is an electric oil pump 410. Oil pump 410 is coupled to an oil bottle conduit 412 at one inlet/outlet fitting 414, wherein oil bottle conduit 412 is in fluid communication with the inside of oil bottle 404. The cap 430 of oil bottle 404 may comprise a foam seal capable of preventing debris, water, etc. out of the interior of oil bottle 404, yet not creating a “sealed” system. With this configuration, oil bottle 404 is not susceptible to temperature fluctuations causing the formation of a vacuum or leading to siphoning effects in the system. Oil bottle conduit 412 extends beyond cap 430 and into the interior of oil bottle 404. Conduit 412 may extend to the bottom of the interior of oil bottle 404, but it is preferred that the opening on conduit 412 be at least several inches above the base. This insures that a minimum amount of oil is left within oil bottle 404 during an exchange, and thus the oil being exchanged may be sufficiently cooled when mixed with oil in bottle 404. In addition, this provides settling space for any debris that may enter the system. In this way, a standard commercial bottle (i.e., the oil bottle purchased by the user at a retailer) may be used. Alternatively, a specialized bottle, such as one made of nylon, thick-wall HDPE or metal could be utilized and thus more readily receive hot oil from the engine.

Another inlet/outlet fitting 416 of pump 410 is fluidly coupled to an engine sump 418 via a sump conduit 420. Within sump 418 and connected to sump conduit 420 is a bent tube 422. Bent tube 422 may be inserted into sump 418 through the existing oil drain plug 424 of the engine and is sized and angled such that its open end is positioned near the center of the oil volume, which is typically near the centerline (or crankshaft) of a vertical shaft engine. This positioning of the bent tube 422 reduces the effects that tilting or angling of the engine will have on the oil level 426 relative to the tube.

In operation, a controller (not shown) onboard the bottle holder 402 or elsewhere on the machine detects whether or not the engine is running. If the engine has not been running for a predetermined period of time (e.g., 5 seconds to 5 minutes), a signal is sent to pump 410 via communication lines 432 to begin the oil exchange process. This process comprises pumping oil from oil bottle 404 for a predetermined period of time (e.g. 1-15 seconds) to transfer a quantity of oil from oil bottle 404 to sump 418 (e.g., 4-20 fl. oz.). After this predetermined period of time has lapsed, the controller then sends a signal to pump 410 to reverse operation and pump oil out of sump 418 of the engine for another predetermined period of time (e.g., 5-30 seconds). The pump 410 will typically run longer when it is pumping oil out of sump 418 than when it is pumping oil into sump 418 to ensure that the engine oil is maintained within sump 418 at the correct level (i.e., approximately the level of the opening on bent tube 422) such that predominantly air is being pumped out of pump 410. Pump 410 is preferably an electric motor-powered gear pump that is able to self-prime, pump air, and easily reverse pumping direction. However, other pump designs may also be used. Alternatively, the controller may determine that the oil level in sump 418 is sufficient by detecting that the current draw of pump 410 has reached a predetermined low threshold amount, signifying that pump 410 is sucking air rather than oil and thus it is safe to turn pump 410 off. The controller could also be configured to allow for a predetermined wait period between pumping oil into sump 418 and pumping oil out of sump 418 so as to allow time for the oil to mix. In this way, a single set of input/output lines can be used between oil bottle 404 and sump 418, oil can be interchanged after engine operation, and the user can be assured that sump 418 maintains the correct oil level after each oil exchange operation. In an alternative construction, a single line extends between the supplemental oil tank and engine. The line would then branch into two separate lines within the engine with one line arranged to draw oil from the engine sump and the second line arranged to add oil to the engine sump. Check valves could be positioned in each line to assure the proper flow in each line.

As an alternative to the process described above, it is also contemplated that the oil exchange process could be activated when an engine's ignition key is detected to be in the “off” position. Likewise, the process could be activated when the ignition key is detected to be in the “on” position, or the fill cycle could be activated when the key is in the “off” position and the drain cycle activated when the key is in the “on” position. Another alternative is for there to be a user-actuated switch to allow the operator to determine when they would like the oil exchange process to be activated.

Turning to FIG. 5, a sectional view of an engine sump and portions of the oil exchange system in accordance with an exemplary embodiment are shown. Engine sump 502 contains oil 504 that is preferably maintained at a predetermined level. A bent tube 506 is attached to a fitting 508 and conduit 510, wherein fitting 508 is designed to fit into the existing oil drain plug opening 512 of the engine. Bent tube 506 is sized and shaped such that the tube can be easily inserted into the plug opening 512 and positioned such that an opening 514 of bent tube 506 is near the center of the engine (and the crankshaft) and is substantially aligned with a preferred oil level within sump 502. Tube 506, fitting 508, and/or conduit 510 are preferably marked to allow the user to determine if bent tube 506 is properly oriented within sump 502. If the orientation of bent tube 506 within sump 502 is not proper, the oil level maintained may not be sufficient. As FIG. 6 shows, during the oil exchange process, an additional amount of oil 516 is added to the sump to be mixed with the oil 504 already therein. After a predetermined period of time (or some other predetermined operation), an amount of oil is pumped out of sump 502 such that the level is again maintained at the level of the opening 512 of bent tube 506.

Additionally, the configuration shown in FIG. 5 could allow for an “oil change” operation as opposed to an oil exchange operation, as described above. In this “oil change” operation, the fitting 508 and bent tube 506 may be clocked or rotated approximately 90 degrees in either direction (for example by a user manipulating a handle provided on the outside of the engine that connects to the tube) such that the opening 514 of bent tube 506 is rotated or moved to then be located near the base of the interior of sump 502. In this position, the pump (not shown) can be used to extract a majority of the oil 504 in sump 502 into the supplemental oil container (not shown). A user-actuated switch could be used to trigger this “oil change” operation, as opposed to the automated approach of the oil exchange operation described above. Such an “oil change” mode would allow for convenient disposal of spent oil, as the user would not have to access the drain of sump 502 for each oil change, but would instead be able to properly dispose of or recycle the contents of the supplemental bottle, or dispose of the supplemental bottle entirely. To complete the overall oil maintenance, the user would simply have to replace the oil filter and add fresh oil back into the engine, doing so either via a fill tube or again via a supplemental bottle and pump. In another arrangement, a more convenient method for performing a complete system oil replacement is possible. In this arrangement, a second conventional drain passage (drain plug or drain hose with cap) on the engine sump 502, cylinder or cover can be opened to allow the force of gravity and the head of oil to drain oil out of the engine. The pump is then operated in the proper direction to pump the remaining oil from the supplemental oil tank back to the engine for draining. In this way both quantities of used oil can be easily drained through only one passage. The old oil filter can be conventionally changed as noted above.

To replace the drained oil, the tank and sump could each be filled conventionally through respective oil fill openings. Alternately, the engine alone is filled with a sufficient quantity of oil to refill both the engine and oil tank to proper predetermined levels. The pump is then operated in reverse to pump any excess engine oil to the oil tank, thereby leaving the engine at the proper full level. Alternately, oil could be added only to the supplemental tank and the pump operated to return the engine to the proper oil level, either in one timed add/drain pumping process or several smaller add/drain cycles. Pump current draw could also be used to detect when the engine has been filled properly, by detecting the timing and/or order of high and low current draw associated with pumping oil and air respectively.

Controller programming and an additional LCD display with user interface buttons could provide step-by-step instructions to guide the user through the oil change drain and/or refill process and activate the pump when appropriate. The display could also show the oil life percent remaining, hours of operation, when the system has completed a refresh cycle, and other useful user updates. Various methods of establishing oil life percentage are possible. A simple “time only” system may be the simplest, but time at load or speed and other oil element detectors could also be used. A sophisticated electromechanical valve system and controller could also be added to help automate the drain process.

Referring now to FIG. 7 and FIG. 8, an oil recirculation system in accordance with another exemplary embodiment is shown. Oil recirculation system 600 is illustrated as being implemented on a ride-on zero-turn radius lawnmower, but it is to be understood that oil recirculation system 600 could be implemented on any appropriate engine driven device including a tractor, electricity generator, pressure washer, construction equipment, outdoor power equipment and the like. System 600 comprises a supplemental oil tank 602.

Supplemental oil tank 602 may be formed of metal, plastic, or any other suitable material. Additionally, the capacity of supplemental oil tank 602 (e.g., 2 gallons) is preferably larger than the capacity of the engine sump. Supplemental oil tank 602 comprises an easily-accessible oil fill cap 603 capable of being removed such that a user can fill supplemental oil tank 603 with engine oil. In the present embodiment, supplemental oil tank 602 is mounted via one or more tank brackets 604 to a transmission fluid cooling structure 606. In some zero-turn radius mowers, transmission fluid cooling structures are mounted above an engine and are configured to accept transmission fluid from one or more hydrostatic transmissions that are used to drive the wheels of the mower. As the fluid flows through the cooling structure, it is cooled and then returned to the hydrostatic transmission. In the present embodiment, because cooling structure 606 is mounted above engine 609, it makes an ideal mounting point for supplemental oil tank 602. However, it is to be understood that supplemental oil tank 602 may be mounted elsewhere on the mower and may be used with mowers that do not utilize a transmission fluid cooling structure.

System 600 further comprises a vent tube 608 which extends from the interior of supplemental oil tank 602 to the crankcase of engine 609. More specifically, vent tube 608 runs from a point near oil fill cap 603 to the engine crankcase so as to maintain a pressure in oil tank 602 equal to or nearly equal to the pressure within the running engine's crankcase. This configuration prevents large pressure differentials between the tank and the engine which may lead to unwanted supplemental oil delivery or extraction via siphoning effects, etc.

Running from the bottom portion of supplemental oil tank 602 is a first oil hose 611, as shown in FIG. 8. If the supplemental oil tank 602 is made of a material capable of withstanding high heat (e.g., metal), first oil hose 611 may be coupled to the bottom portion of tank 602 such that no portion of first oil hose 611 protrudes into the interior of tank 602. In this configuration, the oil within tank 602 can be completely drained. On the other hand, if supplemental oil tank 602 is formed of a material not capable of withstanding high heat (e.g., plastic), first oil hose 611 may protrude a certain amount into the interior of tank 602 such that a certain level of “cool” oil is always maintained within tank 602 as described above in reference to FIG. 4.

First oil hose 611 runs from tank 602 to an inlet of an anti-siphon chamber 618, where a second oil hose 612 is coupled to the outlet of anti-siphon chamber 618. Anti-siphon chamber 618 is configured to prevent oil from being unintentionally siphoned from tank 602 to the sump of engine 609. To achieve this, anti-siphon chamber 618 is designed to have a larger diameter than the diameter of first oil hose 611 and second oil hose 612 and is mounted on the mower or other device at a point higher than the level of oil within tank 602. In addition, the volume of the anti-siphon chamber 618 that is disposed above the oil level in the supplemental oil tank 602 should be larger (e.g., 1.2-2 times larger) than the internal system volume of the various hoses and other fluid containing devices between the anti-siphon chamber 618 and the engine sump 602. The anti-siphon chamber 618 has a 180 degree bend at a top portion such that the chamber 618 is located near the uppermost section of the oil path between tank 602 and engine 609. At least a portion of anti-siphon chamber 618 is mounted above the oil level, even when tank 602 is tipped to an extreme operating angle (e.g., 30 degrees). Alternatively, the chamber 618 may have straight or other angled fittings that position it high within the hose path. As anti-siphon chamber 618 is higher than the oil level within tank 602, the oil's natural tendency to maintain the same level throughout the system (i.e., in both the tank and the hoses) does not cause the oil to flow out of chamber 618 when the flow of oil is not desired. Additionally, the angle of the mower (and subsequently tank 602) does not cause oil to flow out of chamber 618 when not desired due to the fact that chamber 618 is mounted at this height.

An electric pump 610 is coupled in-line with second oil hose 612 and is operational to both pump oil from supplemental oil tank 602 to the sump of engine 609 and, conversely, to pump oil from the sump to supplemental oil tank 602. Electric pump 610 is preferably a gear pump but may be any appropriate fluid pump. For example, electric pump 610 could also be a positive displacement pump. A coupling 614 is placed in the oil drain port of engine 609 to fluidly couple oil hose 612 to a sump tube assembly 616 that is inside the sump of engine 609. Sump tube assembly 616 preferable extends upward and into the sump of engine 609 such that its outlet is near the center of the sump and is a predetermined distance (e.g. several inches) above the base of the sump. This location of the outlet of sump tube assembly 616 prevents variations in oil level due to the angle of engine 609 when oil is being added to or removed from the sump. Additionally, in this embodiment, the outlet of sump tube assembly 616 preferably sprays the oil laterally away from sump tube assembly 616 such that the oil added to the sump is better mixed with oil already within the sump, thereby preventing this “new” oil from easily being pumped out of the sump during the oil exchange process.

Referring still to FIG. 7 and FIG. 8, system 600 further includes a control module 620 that acts to control the timing of an oil exchange sequence to and from tank 602 and the sump of engine 609. Control module 620 may be mounted in any appropriate location on the mower or other device. In the embodiment shown in FIG. 8, control module 620 is mounted in a housing near the operator's armrest, and FIG. 7 shows that control module 620 further controls an LED indicator light 622, which is illuminated when the oil exchange sequence is taking place. In some constructions, a tilt-angle sensor is employed to detect the angle of the lawnmower or other components of the system. The tilt-angle sensor provides data to the controller that is indicative of the angle of the device. The controller is then programmed to prevent oil transfers when the tilt angle exceeds some predetermined value (e.g., 10 degrees). The use of the tilt-angle sensor reduces the likelihood of inaccurate measurements or transfers of oil due to the angle of the system.

In the present exemplary embodiment, control module 620 detects when the engine has been shut down for a predetermined period of time (e.g., 6-10 seconds). If that period of time has elapsed without the engine being restarted, control module 620 instructs pump 610 to begin pumping oil from supplemental oil tank 602 into the sump of engine 609 via oil hose 612 for another, second, predetermined period of time. When this second predetermined period of time has elapsed, the system waits for a third predetermined period of time to allow the oil within the sump to mix and settle, and then control module 620 instructs pump 610 to reverse and pump oil out of the sump and into the supplemental oil tank 602 via the same oil hose 612 for a fourth predetermined period of time, wherein the fourth predetermined period of time is longer than the second predetermined period of time. In an alternative embodiment, the fourth period of time may be equal to the second period of time. With this configuration, an oil exchange process that allows for extended intervals between general engine service tasks is possible. In another alternative embodiment, control module 620 may include electronics configured to sense the angle of supplemental oil tank 602 and engine 609 and to prevent pump 610 from cycling when the angle is equal to or greater than a predetermined amount. This configuration reduces the potential for under-filling or overfilling the sump of engine 609 due to the angle of the system. The system may further comprise an extended-performance oil filter 624, which allows for these extended intervals.

It should be noted that the movement of oil from the supplemental tank to the engine sump and from the engine sump to the supplemental tank occurs in conjunction. Thus, the order in which the oil is moved is not critical so long as movements in both directions occurs, thereby assuring that the desired level of oil within the oil sump is maintained.

The system described herein is described in use with a lawn mower. However, the system could be employed with virtually any system that includes an oil-lubricated engine and more particularly an oil-lubricated internal combustion engine. For example, stand-by generators (residential and commercial) as well as remote power generators (e.g., cell towers, remote pumping stations, etc.) often employ an oil-lubricated engine and would benefit from use of the system described herein. As such, the invention should not be limited to only lawn mower applications.

Although the present disclosure has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the defined subject matter. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present disclosure is relatively complex, not all changes in technology are foreseeable. The present disclosure described with reference to the example embodiments and set forth in the following definitions is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the definitions reciting a single particular element also encompass a plurality of such particular elements.

Various features and advantages of the invention are set forth in the following claims. 

What is claimed is:
 1. An oil recirculation system, comprising: an engine lubricated by a flow of oil through the engine; a supplemental oil tank arranged to contain a quantity of oil; an oil inlet conduit arranged to fluidly connect the supplemental oil tank and the engine; an oil outlet conduit arranged to fluidly connect the supplemental oil tank and the engine; a first pump operable to pump oil from the supplemental oil tank to the engine through the oil outlet conduit; and a second pump operable to pump oil from the engine to the supplemental oil tank through the oil inlet conduit; wherein the oil inlet conduit is coupled to the supplemental oil tank at a location above where the oil outlet conduit is coupled to the supplemental oil tank.
 2. The oil recirculation system of claim 1, wherein the supplemental oil tank further comprises an oil drain separate from the oil outlet conduit, and wherein oil can be selectively drained from the supplemental oil tank through the oil drain.
 3. The oil recirculation system of claim 2, further comprising an oil vent conduit coupled to the engine and the supplemental oil tank and configured to equilibrate pressure between the engine and the supplemental oil tank.
 4. The oil recirculation system of claim 1, further comprising an oil filter.
 5. The oil recirculation system of claim 1, wherein the supplemental oil tank is disposed at least partially above the engine.
 6. The oil recirculation system of claim 1, wherein the engine includes an engine sump and the capacity of supplemental oil tank is larger than the capacity of the engine sump.
 7. The oil recirculation system of claim 1, wherein the first pump is positioned in-line with the oil inlet conduit, and wherein the second pump is positioned in-line with the oil outlet conduit.
 8. The oil recirculation system of claim 1, wherein the first pump and the second pump are positive displacement pumps.
 9. The oil recirculation system of claim 1, further comprising: a seat arranged to define a forward and a rearward direction, wherein the engine and the supplemental oil tank are located rearward of the seat.
 10. The oil recirculation system of claim 1, wherein the supplemental oil tank is made of metal.
 11. A ride-on mower, comprising: an engine lubricated by a flow of oil through the engine; a supplemental oil tank arranged to contain a quantity of oil; a seat arranged to define a forward and a rearward direction of the ride-on mower, wherein the engine and the supplemental oil tank are located rearward of the seat; an oil inlet conduit arranged to fluidly connect the supplemental oil tank and the engine; an oil outlet conduit arranged to fluidly connect the supplemental oil tank and the engine; a first pump operable to pump oil from the supplemental oil tank to the engine through the oil outlet conduit; and a second pump operable to pump oil from the engine to the supplemental oil tank through the oil inlet conduit; wherein the oil inlet conduit is coupled to the supplemental oil tank at a location above where the oil outlet conduit is coupled to the supplemental oil tank.
 12. The engine of claim 11, wherein the supplemental oil tank further comprises an oil drain separate from the oil outlet conduit, and wherein oil can be selectively drained from the supplemental oil tank through the oil drain.
 13. The engine of claim 12, further comprising an oil vent conduit coupled to the engine and the supplemental oil tank and configured to equilibrate pressure between the engine and the supplemental oil tank.
 14. The engine of claim 11, further comprising an oil filter.
 15. The engine of claim 11, wherein the supplemental oil tank is disposed at least partially above the engine.
 16. The engine of claim 11, wherein the engine includes an engine sump and the capacity of supplemental oil tank is larger than the capacity of the engine sump.
 17. The engine of claim 11, wherein the first pump is positioned in-line with the oil inlet conduit, and wherein the second pump is positioned in-line with the oil outlet conduit.
 18. The engine of claim 11, wherein the first pump and the second pump are positive displacement pumps.
 19. The engine of claim 11, wherein the supplemental oil tank is made of metal. 